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~10 degree difference between upstairs and downstairs rooms

duffeymt | Posted in General Questions on

I live in a 2 story single family ~1700 sq foot home where there is an uncomfortable 10 degree difference between the floors in the winter (too cold upstairs) and the summer (hot as hell upstairs).

We have a single thermostat on the main floor. Setting it to 72 in the winter leaves the upstairs around 65 and a sole bedroom in the front corner of our house is a few degrees cooler than that. That bedroom is what I need to address and it only has a single duct running to it. The temp slowly drops as the night goes on, leaving it quite chilly the next morning.

Attic currently has a low R-19 level.

I am considering a few options but its very difficult to navigate.

1. Identify leakage points in the attic (and house overall) and address plus add insulation in attic to minimum R-49
2. Install dampers for a multi-zone setup so the upstairs bedroom can continue to get heat (worried about a bypass being installed)

I am assuming that option 2 will no doubt keep the bedrooms (and other zones) comfortable since the desired temp should be reached, but should I also insulate so any leakage and heat transfer can be slowed to reduce system usage?

Which one should I “try” first?

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  1. GBA Editor
    Martin Holladay | | #1

    In general, it's always better to invest first in air-sealing work and insulation improvements. These efforts will immediately improve comfort while lowering your energy bill.

    If you tweak your heating system to send more heat to your cool bedrooms -- without making any air-sealing or insulation improvements -- your energy bills will go up, not down.

  2. Expert Member
    Dana Dorsett | | #2

    If you air seal the upstairs rooms and double or triple the R value of the attic insulation it's likely to fix most of the wintertime temperature balance issues.

    If the cold bedroom only has a supply duct and no return it may be a return path problem when the door is closed. A well designed duct system would have supplies and returns matched within every doored-off space, or at a bare minimum guaranteed return paths of adequate size. Using a partition wall stud bay as a jump duct, with a grille near the floor on the bedroom side and a grille near the ceiling on the hallway/other (?) side may get it to balance reasonably with the other upper floor rooms.

    Sealing the ducts (where there is access) with duct mastic, and sealing the register boots to to the subflooring everywhere can also improve overall through put to the upstairs. Typical duct leakage is ~15-20% on unsealed systems, but 40% isn't rare. If the upstairs is only getting 60% of the designed flow, it would definitely run cold.

    Zoning ducted systems is fraught with issues, and not a great DIY project (even the pros screw that up regularly.) Think of it as a last-resort after all else has failed. Even in the best implementations the addition of zoning increases air-handler driven outdoor air infiltration, increasing energy use. It's only a matter of how much that energy use increase is.

  3. duffeymt | | #3

    Thank you for the helpful replies!

    What do you guys think about getting tests done for duct leakage and using an Aeroseal application?

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